Understanding TLC NAND
by Kristian Vättö on February 23, 2012 1:14 PM EST- Posted in
- Storage
- SSDs
- OCZ
- Indilinx Everest
- TLC
Our thoughts are a bit mixed. On the one hand, cheaper SSDs are exactly what consumers want. The performance is still there compared to hard drives, no matter what NAND is used. If you go to an Apple Store today and try out MacBook Air and Mac Pro, the MacBook Air will often feel faster, even though it's the slower Mac in terms of processing power. This is solely due to the presence of an SSD. An SSD can bring new life to a computer that is otherwise considered obsolete. That's why we think everyone would want an SSD, but it's understandable that the masses won't adopt SSDs until the price and capacities are reasonable. This is definitely where TLC shines—it provides us with noticeably cheaper SSDs, possibly cheap enough for the masses to adopt (e.g. well under $1 per GB).
On the other hand, we're concerned that the cut in prices is done at the expense of endurance. One advantage often heard about buying an SSD is that SSDs are a lot more reliable than hard drives. In terms of P/E cycles, that is probably true with current MLC NAND. However, there have been quite a few widespread firmware issues, such as SF-2281 BSOD and Intel 320 Series 8MB bugs. Those have been fixed, and we may finally be looking at SSDs which have good performance, adequate endurance, and are more or less trouble-free. However, TLC will require new controller logic, and new logic may result in additional firmware issues.
The earliest SSDs lacked performance, even though they were faster than most hard drives, especially in seek times. In just a few years, performance has increased exponentially, maybe even to a point where the average user won't notice the difference between the fastest SSD and a mediocre SSD.
Given the desire for performance, reliability, and cost, TLC NAND may take away one from the triplet: endurance. Notice we said "may", because P/E cycles aren't everything. It has been claimed that algorithms to minimize write amplification will follow Moore's Law, just like NAND does. In other words, every time there is a die shrink, wear leveling has been improved in order to keep endurance the same. On top of that, improvements in manufacturing technologies can keep the P/E count up as well. 20nm IMFT MLC is claimed to have 3000-5000 P/E cycles, just like 25nm IMFT MLC.
The good news is, MLC NAND will stay in production and hence MLC NAND based SSDs are not going anywhere. What TLC will provide is freedom of choice. If you use your computer for checking email and browsing the Internet, no doubt a TLC based SSD will be sufficient. For the majority of consumers, TLC SSDs should meet their demands.
In addition, the SSD market is evolving quickly; if you buy the best SSD today, it won't be the best for very long. Let's say that it lasts you for four years. In that time, the SSD market will change a lot—four years ago, we were looking at 16GB SSDs for nearly $600! By the time a typical SSD is ready for replacement, you will be looking at much faster SSD with more capacity, and likely for a lower price. In 4.5 years, we have gone from that 16GB offering with performance that often trailed behind contemporary HDDs to 120GB SSDs that are up to a couple orders of magnitude faster than HDDs on random access patterns (and still several times faster for sequential tranfers), all for a starting price of around $170. If that pattern holds for the next four years, we'll be looking at ~1TB SSDs in four years that offer transfer rates that would saturate multi-lane PCIe interfaces at even lower prices. While we expect the rate of progress to be quite a bit slower over the next four years, there's still plenty of room for improvements in SSD technology.
As far as TLC-based SSDs are concerned, all we can do now is to wait for the first product announcements to come. Once we get some review samples, we'll be sure to put them through our SSD test suite and see how they stack up to existing drives.
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BPB - Thursday, February 23, 2012 - link
I just ordered the OCZ Synapse to use as a caching drive. The reviews all rave about speed increases. I am putting it in my main system. Would be nice if you could tell us where they fit in.Also, anybody got recommendations on an SSD to get an older system to feel faster for surfing and the like?
Kristian Vättö - Thursday, February 23, 2012 - link
It's hard for me to say anything about caching SSDs because we haven't reviewed any other than Intel 311 Series (yet). IIRC Synapse comes with its own caching software which is different from Intel's SRT.Fortunately, we have some more staff working on SSD stuff now. As you may have noticed, so far Anand has done all the SSD reviews. To reduce Anand's workload, I'll be doing some of the SSD reviews in the future, which should allow us to review more SSDs. In fact, I have Plextor M3 SSD on its way here :-)
As for the SSD for an older system, is it a desktop or laptop? I think the best option would be a SSD+HD combo because that is cheap and still lets you have a decent amount of storage. You can try to find older SATA 3Gb/s SSDs (e.g. Intel X25-M G2 or Samsung 470 Series, they are very reliable). You can even hunt for a used drive, some people are already switching for faster SATA 6Gb/s SSDs so you may find a bargain.
ckryan - Thursday, February 23, 2012 - link
Synapse comes with NVELO's dataplex caching software, and there should be more consumer target caching solutions out soon.macuser2134 - Friday, February 24, 2012 - link
An upcoming Plextor M3 review - this is exciting! It will certainly be interesting to find out how a Plextor drive compares to other manufacturers.As a side note the "Pro" version of the Plextor M3 just started selling on Newegg only 2 days ago. Models PX-128M3P, PX-256M3P etc.
seanleeforever - Monday, February 27, 2012 - link
there is something else the articles did not address. the life time of a certain SSD device is a combination of its cell reliability and how often it get re-written to.take a look at the second page, it may look like at 3x nm, the SLC can last 20 times more than MLC. However, from a device point of view, a 120 GB SLC can well last 40 or more time than a 120 GB MLC because as you write and delete file over and over.
for example, in order to re-write the entire 120 GB of information, each cell of the SLC only get erase-write once while a 120GB MLC will most likely been erased-write twice (say to change 11 to 10 to and to 00 , a SLC will need to erase and write once on each of two cells where MLC will need to erase and write at least 3 times on a single cell), or try to imagine a super MLC cell that has all the voltage level needed for 120GB storage in one cell, then every-time something is changed that cell get re-written.
this just get a lot worse in TLC design, as you reduce the number of cells to realize more storage space, you are reducing the error margin as well as increasing the cycles. the old saying still applies "there is no displacement for replacement". there is no free lunch.
BPB - Friday, February 24, 2012 - link
Thanks for the reply. I'll look into your suggestions, though given what I understand to be the limited life of SSDs I think I'll go new. Thanks again.Shadowmaster625 - Friday, February 24, 2012 - link
Please keep an eye out for caching solutions such as NVELO's dataplex caching software. I am looking for one that works with XP. It doesnt make much sense to have to upgrade the OS if all you're looking for is a cheap upgrade to a 5 year old pc. $69 for a caching drive is one thing. $220 for a drive and an OS is quite another...JNo - Friday, February 24, 2012 - link
Agree. I mentioned the NVELO caching software on these boards weeks (maybe months) ago after storagereview looked at them. It would be really good if you got some of their drives or even just software in to review. It is exciting that there is a competitor to Intel's caching in this space. Who knows? They may even be faster, cheaper and better....xrror - Monday, February 27, 2012 - link
I'd also like to see some analysis on NVELO "solutions." I was looking pretty seriously at buying Corsair's version of this with their Accelerator series drives as an "impulse purchase" but lack of availability of their 60Gb package and a good read of NVELO's software "licensing" put a quick halt on that.NVELO looks like a killer app assuming it works. Sadly I expect that it does live up to it's claims, but their DRM is pretty harsh. It's locked to your hardware, so if you say change your video card you must "re-activate."
I know that for most people that's no worse than windows itself, but I change hardware a lot, and/or I'd like to be able to move the SSD cache to other machines in my house w/o worrying that I'll get DRM lockout.
Roland00Address - Thursday, February 23, 2012 - link
57 months ago (4.75 years) you could get a 16gb supertalent for 600 dollars41 months ago (3.41 years) you could get a 80gb intel (1st gen) ssd for 600 dollars.
Small deviations make a big difference when you are calculating exponential growth (and decrease)